Movement transmission system for measuring instruments



Aug. 15, 1944. R. I. N. WEIN G ART MOVEMENT TRANSMISSION SYSTEM FOR MEASURING INSTRUMENTS Filed Apiil 24 1945 WTOK.

A Patented Aug. 15,

UNITED STATES PATENT orr ca uovmimnr 'rasnsanssron srsrm ron amssonnvc INSTRUMENTS mm x. N. Weingart, Glen Head, is. 2.

Application April 24, 194:, Seth-l No. mass SCIaims.

comprises a helical element carried on the pointer shaft, and a substantially sector'shaped drivinc gear which is connected with the responsive element. such as a Bourdon tube, bellows, or the like, "the gear having a single, elongated drivin face which is disposed generally to the lead angle of the helical element, and which contacts such helical element. A movement of this type is disclosed in Patent No. 2,294,869, and provides a driving gear for turning the pointer shaft in one direction, and a hair spring to turn it in the opposite direction as such opposite rotation is permitted by opposite rotation of the driving gear.

The present invention relates to an improved movement of this general type wherein friction of the moving parts is considerably reduced. One of the objections to a movement of the kind dis closed in the aforementioned patent resides in the fact that both the driving shaft and the driven shaft have a thrust longitudinal of their axes, since the driving gear exerts a thrust on the helical element longitudinally of its axis during the driving operation. This thrust is op-' posed by a thrust bearing, as shown in this pateat. It is an object of the present invention to provide an improved structure wherein suchlonsltudinal thrust is not transmitted to either shaft, and wherein the movement has a high degree of accuracy and a long life.

Another object of the invention is to provide wherein the thrust longitudinally of the axis of the helical element is opposed by a second, generally sector-shaped gear member, which con-. tacts a thrust surface associated with the helical element, and which rotates with the driving gear, thus providing a true rolling action between such second or supporting gear and the thrust surface, just as is provided between the driving-gear and the helix element. accordance with the foregoing eliminates all longitudinal'thrusts on both the driving and the driven shafts. eliminates a major portion of the friction on the bearings and other moving parts which is a necessary incident of the movement of 55 (c1. la-151) the patent referred to, and the movement is only slightly aifected by vibration.

- The peripheral driving edge of the driving' gear should be an element of a cylinder if true rolling action is to be obtained. The peripheral supporting edge of the supporting gear is likewise ,an element of the same cylinder, and its entire drivingedgeliesinoneplanewhichisatright angles to the axis ofthe driven shaft. Any

0 variation of the peripheral edge of the supporting gear from this plane'produces, when'the sup porting gear is rotated, movement of the thrust surface and the helix lohlltudinally of their axesr 'niis longitudinal movement causes rotary action in the helix and its driven shaft inde-- pendent of such rotary action caused by rotation of the driving gear, resulting from screw action between the driving gear and the helix, and this action may be'used in calibrating the instrument in which the movement is used.

Another object of the invention is to provide a movement transmission system of the character described wherein calibration can be. accomplished without changing the surface of the driving gear. The supporting gear is formed of sheet metal or other bendable material, and the contour of the peripheral edge may accordingly be varied to accomplish this calibration.

A further object of the present invention is 6 the provision of a movement transmission system for measuring instruments wherein the driving element comprises a plurality of driving gears,

- one of such gears exerting a thrust against the helical driven element. and the other of such gears supporting the helical element, thus receiving the longitudinal thrust on the helical element, the second gear also imparting frie tional driving action to the driven lncmber.

Another object of the present invention is the an improved movement of this general character. provision of movement mum a ing shaft, driven shaft, and driving and driven gears, and wherein' movement of the driving 'shaft longitudinally of its axis does not impart rotation to the driven shaft. Yet another object 4 of the invention is to provide a movement wherein .a driven helical element will be restrained from movement longitudinally of its axis with relation to its driving element when subjected to vibration or shock.

A movement constructed in so In the drawing:

of Fig. l, the view not showing the frame elements.

Fig. 3 is a detailed side elevation of the lower end of the helical driving element and the supporting gear.

Fig. 4 is a perspective view of a modiiied form of combination driving gear and supporting gear.

Fig. 5 is a broken plan view showing a modifled form of restraining means for the driven element.

The structure illustrated in Figs. 1, 2 and 3 includes a Bourdon tube I l mounted in a socket II and provided at its free end with a pivoted link l2. The driving portion of the movement comprises a lever it which is substantially centrally mounted on a shoulder portion ll formed on shaft it. One end of lever It is provided with a plurality of spaced holes It, one of such holes receiving a pivot pin II at one end of link II. The several holes are for purpose of calibration. At the opposite end of the lever II, the driving gear ll 'is carried. The peripheral driving, edge II of the gear is an element of a cylinder, and such driving edge is generally disposed to the lead angle of the helical element which will presently be described. This arm l3 and driving gear 2i may. if desired, be formed from a single blank of sheet metal, and the driving face appropriately twisted to the proper contour.

Shaft I5 is iournalled in' frame members 20 and 25, as is driven shaft 28. The helical element 21 is mounted on, and keyed to, the driven shaft, and in this instance is shown as being formed from a cylindrical blank of metal rod having the spiral recess 2| cut therein. In this arrangement,, the driving face of the gear II is the lower marginal edge of such gear. which edge contacts the lower surface of the spiral recess.

, Clockwise rotation of the pointer II and pointer shaft 28 is imparted by hair spring ii, and counter-clockwise rotation of the shaft is caused by driving gear l8.

Movement of driving gear ll acting against the face of the spiral imparts a force against the face of the helical element, which has several components, one of which acts in a direction parallel with the of the helix. This thrust is opposed by the following novel mechanism. A second gear I! is' also carried by, and is'secured to, a shoulder H, but is spaced from lever It by means or a sleeve 2! carried on shoulder I. The marginal edge." of this gear is an element of the same cylinder as is driving gear ll,so that such edge is a projection of edge Ii, lying, however, in a single plane at'right angles to the axis of rotation of the driven shaft. The particular means for mounting gears It and 35 on shaft I5 is, of course, a matter of choice, it being only necessary that each of these gears be rigidly mounted on the shaft and rotate together. This edge of gear 3' contacts a thrust member I. carried on the driven shaft 28 and formed with a tapered lower or thrust surface 3!, which has the general contour shown in Figs. 2 and 3.

Helical element 21' was earlier described as being mounted on, and keyed to. shaft 26-. If preferred, however, the structure illustrated in Fig. 2 may be employed wherein the helical element is formed-integrally with the shaft. In the event that the spiral recess 28 terminates short of the terminal of the helical element 21, thrust member 38 may then he formed integrally with the helical element and the shaft. In accorda,ses,eee'

, ance with common practice, however, the spiral should preferably be sufllcient to provide a point contact between the driving edge 36 of supporting gear 35 and the thrust surface 39, since if there is a surface engagement between gear 3! and. this thrust-bearing surface 39, a certainmeasure of friction is caused. It will be obvious. however, that the point contact is preferable. The angle of surface 38 should desirably be sumcient to permit of calibration of the'instrument by means of varying the contour of driving edge 38 of gear 35. This calibration may, of course, be effected by two means, either the bending of the driving edge out of a plane at right angles to the axis of the driven shaft, as shown by dotted lines .40 in Fig. 2, or by so forming the peripheral edge 3! in a manner not to constitute an element of a'true cylinder, in which case longitudinal'motion of the driven shaft will be caused as that portion of the driving edge approaches or.recedes from the element of a true cylinder.

Commercially, however, it is advisable to make both driving edges 2! and 30 elements of the same cylinder, and accordingly the pitch-line velocity of driving edge 2! of gear II is the same as the pitch-line velocity of the face of the recess 2! which it contacts. The same .is true 0! the respective pitch-line velocities of driving edge 36 of gear 35, and of that portion of thrust surface 39 which it contacts. By forming the driving edge 36 of gear 35 and the thrust surface 39 in this manner, gear 35 in addition to providing its supporting function, which is of the utmost importance, also imparts frictional rotation to the thrust surface, and accordingly to the driven shaft. This fact accounts for a further ing parts. Gears II and II have been described .as formed from sheet metal, although an alternative form is shown in Fig. 3 wherein supporting gear 35 is formed with a non-metallic element 44 having a driving edge ll which again makes the point contact with thrust surface 39. This non-metallic element or facing, which considerably reduces wear between the parts, may be formed from plastic material, or any other suitable materlal.

In Fig. 4, an alternative form of gear is pro-.- vided wherein the driving gear, the supporting gear, and the lever are formed from a single piece of sheet metal. In this instance, the lever 4! is formed with an aperture 0 which receives the supporting shaft, and with a plurality of apertures 50, one of which receives the pin at the free end of the-link which is connected with ment, is generally tangent-'to'such element at the point of contact. As the gear rotates toward one of its terminals or the'other, the plane of such gear assumes a more acute or obtuse angle relative to the driven face of the helical element at its then point of contact, depending upon its direction of rotation. Accordingly, it is diillcult to deilne this varying relationship of the peripheral driving edge of the gear to the helical element. For convenience of expression, this relationship is referred to in the appended claims as one in which the peripheral driving edge is generally disposed to the lead angle of the helical element. In the theoretical or ideal state, the

driving element in a movement such as herein described is a helix ofllarger diameter than that of the driven element, but having the same lead I a V a driving gear formed with a driving face which contacts the helical element and produces rotation thereof by exerting a thrust against the helical surface, a driven shaft associated with the helical element, pivotal means for mounting the driving gear and means connecting the. driv-' ing gear with the condition-responsive means,

and means for opposing movement of the shaft angle as the helical driven element. In this case,

it would be truly disposed, i. e.. tangent, to the driven element throughout its length.

A modified form of means for restraining movement of the driven element longitudinally of its axis is shown in Fig. 5. In this case, the

driven element 55 is formed with the spiral recess l8 and carries a shaft terminal 51. The thrust element, in this case, comprises 'a circular memher I! having an annular recess It therein, thus Supporting forming opposed thrust faces I. gear '2 in this instance may contact both of these thrust faces, thus restraining longitudinal movement of the driven element in either direction. This arrangement is particularly success- .ful in cases wherein the driving gear presents a true helical surface and contacts the opposed faces of the spiral rece, thereby driving the helical element inboth directions. It is also important in restraining such movement of the helilongitudinally of its axis comprising a thrustreceiving element carried by the shaft and a second gear associated ,with the driving gear con- I tacting said thrust-receiving element.

- 3. A movement for a measuring instrumen having means responsive to changes in conditions, said movement comprising a driven shaft, a helical element associated with the driven shaft, a pivoted driving gear formed with a gear face which exerts a force against such helical e1ement to rotate the'same, means connecting the driving sear with the condition-responsive element,'a thrust element positioned on the driven shaft, and a supporting gear carried by the driving gear and formed'with a face which contacts the thrust element and opposes longitudinal movement of the shaft.

4. A movement for a measuring instrument.

having means responsive to changes in conditions,

cal element longitudinally of its axis as maybe caused by shock or vibration. The supporting gear 62 may, in thiscase, or in any other case,

be formed integrally with the driving gear, as shown in lj'ig. 4. Likewise, it is important to point out in connection with the structure shown in Fig. can: if gear SI is used as the. supporting gear,-it may lie on the same plane as lever 48, eliminating the necessity of twisting the same.

In this case, gear I! will be the driving gear and will lie at an angle generally disposed to the helical driven surface.

The several embodiments of the invention shown and described herein are for purpose of illustration only and are not ,to be taken in any limiting sense. It will also be apparent that many changes and modifications may be made in the structures illustrated and described without departing from the spirit of the invention,'as defined by the appended claims.

What I claim is: 1

i. A movement for a measuring instrument having means responsive to changes in condi tions, said movement comprising a shaft. a hellcal driven element associated with said shaft, and a driving gear for driving the driven element, means connecting the driving gear with the condition-responsive means, and means for restraining movement of the drivenelement longitudinally of its axis comprising a thrust element carried by the shaft and a second gear movable with the driving gear, contacting said thrust element.

2. A movement for a measuring instrument having means responsive to changes in conditions, said movement comprising a helical driven said movement comprising a driven shaft carrya ing a pointer, a helical element associated with the driven shaft, driving meanscomprising a plurality of gears, a shaft upon which said gears are carrled, both of said gears having driving edges which constitute elements of the same cylinder, the driving edge of one of such gears being disposed generally to the lead angle of the helical element and contacting a face of such element,

and causing rotation thereof in one direction by exerting a force against such helical element;

one component of such force being a thrust parallel with the axis of such element, spring means for rotating the helical element and the pointer shaft in the opposite direction, means foropposingsuch thrust parallel to the axis of the helical element and driven shaft, comprising the second gear and a thrust element carried by the shaft, the second gear contacting such thrust element, and means connecting the driving gears with the condition-responsive means.

' 5. A movement for a measuring instrument having means responsive to changes in conditions,

said movement comprising a driven shaft, a helical element associated with the driven shaft, a pivotal driving gear formed with an elongated gear face lying on an angle generally disposed to the lead angle of the helical element, and exerting a force on'such helical element to rotate the ,same in one direction, and spring means for rotating the shaft in :the opposite direction,

- means connecting the driving gear with the conelement and a driving element. comprising a u dition-responsive element, a thrust element associated with the driven shaft, and a supporting gear carried by the driving gear and formed with a driving face lying in a single plane at. right angles to the axis of the drivenshaft, such. drivmounting the driving gear and means connecting the driving gear with the condition-responsive means, spring means for rotating the driven shaft-in one direction, the driving gear rotating said shaft in the opposite direction by exerting a force against the helical element, and means for opposing the thrust parallel to the axis of the helical element caused by such force, comprising a thrustreceiving element carried by the shaft, and a second gear carried by the gear shalt con- 4 tacting said thrust-receiving element;

game

longitudinally oi'its axis. comprising a thrust element carried by the driven shaft. the second gear contacting such thrust element. i

8. A movement for a measuring instrument having means responsive to changes in conditions,

said movement'comprising a driven shalt, a helical element associated with the driven shaft, driving means comprising a plurality of gears,

' means connecting such sears with the conditionresponsive element, a shaft upon which said gears are carried, the driving edge of one 01' such gears being disposed generally to the lead angle of the helical element and contacting the face of such element. and causing rotation thereot by exerting a thrust against such (ace, and means tor controlling movement of the helical element longitudinally oi its axis, comprising a thrust element carried by the driven shaft and having anannular recess therein, the second gear contacting the recess in such thrust element. thus limiting longitudinal movement of the driven shaft to that permitted or caused by the second gear.

mom I; N. wmoaar. 

